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Manganese dioxide (MnO2) is a promising cathode for aqueous Zn batteries owing to its high theoretical capacity and operating voltage. However, it is still confronted with poor conductivity, structural collapse, sluggish ion kinetics, and Jahn–Teller (J–T) distortion. Herein, we propose hydrogen bond-modulated MnO2 by introducing NH4+ (NHMO) for prominent zinc-ion storage. The formation of a hydrogen bond in MnO2 reduces its layer spacing, presenting a more stable structure. The theoretical calculation results demonstrate that the pre-intercalation of NH4+ can effectively reduce the bandgap of the MnO2, enhancing its conductivity. More importantly, the formation of the hydrogen bond can significantly decrease the variation of Mn–O bond length and the proportion of Mn 3dz2 orbitals, meaning that the hydrogen-bond chemistry can effectively suppress J–T distortion. As expected, a high capacity of 287.9 mA h g−1 at 0.1 A g−1 and an ultrahigh rate performance (99.4 mA h g−1 at 6.0 A g−1) can be achieved for the NHMO, as well as a fantastically outstanding cycling stability of 90.0% after 13 000 cycles, far exceeding previously reported Mn-based materials. The rational introduction of a hydrogen bond provides a novel strategy for the development of ultralong lifespan aqueous Zn batteries. [ABSTRACT FROM AUTHOR]

The heat exchanger plays a key role in the S-CO2 power cycle of power generation systems based on waste heat and has a large impact on their cost control and compactness. In this paper, we take the channel shape of a microchannel heat exchanger as the research object and combine orthogonal tests and numerical simulation, taking the microchannel cross-section length/short-axis ratio, volume ratio and filling rate as independent variables, to numerically study multi-channel thermal–fluid–solid coupling and explore the effects of different microchannel cross-section length/short-axis ratios, volume ratios and filling rates on the thermal hydraulic and mechanical properties of the heat exchanger. The results show that a change in the channel volume ratio has a greater impact on the thermal hydraulic performance of the heat exchanger and that its heat transfer performance is only marginally affected by a change in the channel filling rate. Additionally, when other geometric parameters are kept to a certain level, the closer the shape of the channel is to a circle, the better its mechanical properties are. Within the range of permissible designs, a change in the channel volume ratio does not have an obvious impact on the mechanical properties of the microchannels, while the channel filling rate has the most significant impact. The most significant effect of the channel filling rate on the mechanical properties occurs through the channel volume ratio. [ABSTRACT FROM AUTHOR]

The flourishing progression of flexible and wearable electronics has driven the ever-growing demand for high-performance fiber-based energy-storage devices. Meanwhile, metal–organic frameworks (MOFs) with high specific surface area and porosity are promising to act as the precursors and templates for high-performance battery's materials. Herein, MOF-derived NiS2 nanoflower arrays (NFAs) grown on carbon nanotube fibers (NiS2 NFAs/CNTFs) were successfully demonstrated to be the cathodes for advanced fiber-shaped aqueous rechargeable (FAR) Ni//Zn batteries. Density functional theory simulation results confirmed that the introduction of sulfur significantly decreased the band gap, achieving an increased conductivity of the materials. Benefiting from the involvement of sulfur and preserved array morphology, at a current density of 4 mA cm–2, the NiS2 NFAs/CNTF electrode can exhibit an extraordinary capacity of 0.45 mAh cm–2 and an ultrahigh discharge plateau of up to 0.41 V. Additionally, the assembled FAR Ni//Zn batteries deliver an energy density of 219.6 mWh cm–3 at a power density of 2.4 W cm–3 and a significant long-term cycling stability. This approach affords some innovative opinions for the design of electrode materials from the aspect of MOF derivatives via restructuring and modification for high-performance energy-storage devices. [ABSTRACT FROM AUTHOR]

Currently, Zn-based catalysts for electrochemical CO2 reduction reactions are limited by their moderate carbophilicity, resulting in low catalytic activity and CO selectivity. To this end, we selected 5-mercapto-1-methylimidazole, a small molecule that possesses the ability to both coordinate to Zn and interact with the intermediates, to modify electrochemically deposited Zn nanosheets. The interaction between them effectively enhances intermediate adsorption by lowering the Gibbs free energy, which leads to an increase of the Faraday efficiency to 1.9 times and the CO partial current density to 3.0 times that of the pristine sample (−1.0 V vs. RHE). [ABSTRACT FROM AUTHOR]

With the rapid advancements of portable and wearable devices, high-efficiency electromagnetic interference (EMI) shielding materials are highly required to eliminate radiated electromagnetic pollution. Ti3C2Tx MXene has shown great application potential as an EMI SE material due to its good conductivity. However, a single-loss mechanism has many limitations. Herein, to enrich the electromagnetic-wave-loss ways, MXene@ZIF-67/multiwalled carbon nanotubes (MWCNTs) composite films were successfully prepared by vacuum-assisted filtration, combined with the introduction of magnetic ZIF-67 anchored on MXene by an electrostatic self-assembly method. The MXene@ZIF-67/MWCNTs composite film (MZ2M8) achieved the best EMI shielding performance of 63.6 dB at 32 μm thickness, and the contribution ratio of the scattering parameters for absorption to reflection, i.e., SEA to SET, was 66.94%, thus achieving high absorption loss. Due to the high aspect ratio of the MWCNTs and the densely stacked "brick–mortar" layered structure, the composite film also exhibited excellent flexibility and mechanical performance, in which MZ8M2 could deliver a high tensile strength of 115.2 MPa, ensuring practical applications in different environments. Moreover, the thermal conductivity of MZ2M8 reached 3.367 W m−1 K−1, realizing the synergistic effect of high shielding efficiency and heat-dissipation performance, and avoiding the phenomenon of heat accumulation caused by the conversion of electromagnetic waves into heat energy. [ABSTRACT FROM AUTHOR]

Phenolic foam (PF) displays excellent flame, smoke, and toxicity (FST) properties and good insulation properties. Nevertheless, the friability and inferior mechanical properties of PF have critically restricted its application in many fields. A series of phenolic foam/silica nanocomposites (MPF) with different silica contents were synthesized by in situ polymerization in this study. During the in situ polymerization process, the synthesis of phenolic resin/silica nanocomposites and formation of chemical bonding between the components were generated simultaneously. The reactive principle between silica nanoparticles and prepolymer was investigated using Fourier transform infrared spectroscopy (FTIR), and the results of FTIR indicated existence of the chemical reaction between them. Meanwhile, silica can act as 'bridge' to form cross-linked network structure. The mechanical, thermal, and friability properties of MPF nanocomposites were characterized. Moreover, the results of microstructure of pure PF and MPFs indicated that the cell size distributions of MPFs are narrower, the cell distributions of MPFs are more uniform, and the cell wall thickness of MPFs is thicker, compared with pure PF. When the content of silica sol was 2 wt%, the compressive strength, compressive modulus, and tensile strength were increased by a factor of 47.37%, 38.55%, and 57.14% compared with that of pure PF, respectively. Furthermore, all MPF nanocomposites exhibited better thermal stability and lower pulverization ratio than that of pure PF., INTRODUCTION High-rise fires have been attracted increasing attention in recent years due to the flammability of polymer foam insulation materials [1]. As one of thermal insulation materials [2-4], polymer foam [...]

To meet the increasing desire for a means of powering wearable and portable devices, the development of high‐performance flexible aqueous rechargeable lithium‐ion batteries (FARLIBs) would be greatly desirable. The design of binder‐free cathode materials with 3D architectures is the key to develop FARLIBs. Herein, self‐standing 3D Ni‐doped LiMn2O4 (NLMO) nanosheets are successfully prepared assembled by nanowall arrays (NWAs) directly grown on carbon cloth (CC) as the cathode for LIBs, which is performed to slow down the dissolution of Mn and the Jahn–Teller effect of LiMn2O4 during the reaction process. The as‐prepared NLMO NWAs/CC electrode delivers a high capacity of 113.27 mAh g−1 at a current density of 1 A g−1, and can also have a capacity retention rate of 81% after 500 cycles at 10 A g−1, both higher than that of pure LiMn2O4. The results of density functional theory simulation demonstrate that the Ni‐doped LiMn2O4 can significantly decrease the bandgap and Li ions diffusion barriers. A quasi‐solid‐state FARLIB is successfully constructed by using NLMO NWAs/CC as the positive electrode and rugby‐shaped NaTi2(PO4)3/CC as the negative electrode, exhibiting remarkable electrochemical performance and flexibility. These results offer a new opportunity for developing high‐performance FARLIB. [ABSTRACT FROM AUTHOR]